I have to say that I've read the instructions no less than a dozen times and got so confused that it's not even funny. I guess it's just the way it's written out that doesn't quite work with my line of thinking. I got my switchblade key done for my 12 STi, and with the leftover key part along with a $25 purchase of a used key on ebay, I was able to make a key/remote combo key for my wife's 11 Forester.

So here's what you need and what we're doing with them:

What you need:

a transponder chip (best taken out from your valet key)

a new key/remote combo Legacy key (because you need the blank key and the remote)

a switchblade blank key (for the shell)

What you're doing is:

pull the transponder chip from the donar key (it's costly to reprogram a new transponder as far as I understand)

put the transponder from the donar into the switch blade key shell (so that this new key will actually start your car)

put the remote into the switchblade shell

take the remote code from remote off the Legacy key and program that into your car (you can register up to 4 remotes at a time, pain in the butt if you mess this up)

now your switchblade key will have a remote programmed, correct transponder, and a blank key ready to cut

get this new key unit to a locksmith and get a laser cut to match your car key

if it starts, then you're all set!

Now since I got the spare blank Legacy key shell from this procedure, I went ahead to ebay and bought a used Legacy key, and all I needed is the remote unit from it so I don't care if it's a used key at all. The one that I bought for my 11 Forester is CWTWBU766. I then programmed this new remote to the car, pulled the transponder chip, and put both into my leftover Legacy key shell, and whola! I got a brand new combo key for my Forester!

Warning:
Be careful when you're cutting the donar key. I guess you could possibly damage the chip but the chances is pretty slim, but the real danger there is cutting yourself if you're not careful. You'll be slicing and pushing the blade in pretty hard so one slip and you'll probably lose half a finger. Make sure you're working on a non-slip cutting mat and a sturdy box cutter blade, exacto does not work (i chipped my exacto blade and never got deep enough)